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D( x )
x = 0
(2*x^-6)/7 = 0
x = 0
x = 0
(2*x^-6)/7 = 0
(2*x^-6)/7 = 0
2/7*x^-6 = 0 // : 2/7
x^-6 = 0
x naleu017Cy do O
x in (-oo:0) U (0:+oo)
5/((2*x^-6)/7) = 0
35/2*x^6 = 0 // : 35/2
x^6 = 0
x = 0
x in { 0}
x belongs to the empty set
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